#4 Bunching of farfield cells in O-type grids

[Lennart]

As far as I can see, the farfield cells in O-type grids are equally spaced, no matter what surface spacing is used at the leading and trailing edge. To fully capture effects in the wake of an airfoil, it might be useful to bunch the cells in the farfield behind the wake, e.g. increase spacing above and below the airfoil, and decrease spacing behind it. It would be great to have an option for this.

[Dan]

With the hyperbolic solver, there is the FUNI option that affects the farfield spacing. Unfortunately, it's not always possible to really improve the wake spacing with this parameter. However, if you switch to the elliptic solver, there is the FDST setting under SOPT. If you set this to a number greater than 1, it will reduce the make the resolution finer at the farfield in the front and back of the domain.

There is also always the potential to use a C-grid instead of an O-grid to improve the wake spacing.